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Technical Paper

Vizualization of Evaporative Diesel Spray Impinging Upon Wall Surface by Exciplex Fluorescence Method

A single diesel spray of n-decane which was miscible with a small quantity of exciplex dopants was injected from a hole nozzle into a quiescent high-temperature and high-pressure atmosphere of nitrogen, and was impinged in a normaldirection upon a flat wall with elevated temperature. This experiment was to serve as a simplified model of the actual state in a combustion chamber of diesel engines. When a thin sheet of laser light from Nd:YAG laser is passing through the cross section of this spray containing its central axis, it is able to generate fluorescent emissions from vapor and liquid phases in this evaporating spray. Then, clear 2-dimensional images concerning the concentration distributions of vapor and liquid phases were obtained simultaneously, by an exciplex fluorescence method using an image-intensifier and a CCD camera system. The dispersion processes of vapor and liquid phases in this impinging spray near the wall were analyzed with an image analyzer.
Technical Paper

Visualization of the Cavitating Flow inside the Nozzle Hole Using by Enlarged Acrylic Nozzle

In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.
Technical Paper

Vaporization Characteristics and Liquid-Phase Penetration for Multi-Component Fuels

The maximum liquid-phase penetration and vaporization behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters (injection pressure, ambient gas condition and fuel temperature) and fuel properties on vaporization behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector.
Technical Paper

Transient Characteristics of Fuel Atomization and Droplet Size Distribution in Diesel Fuel Spray

The purposes of this study are to clarify the atomization mechanism, the change over time in droplet size distribution, and the change in spray characteristics dependent on back pressure on diesel fuel spray. Diesel spray injected into a quiescent gaseous environment under high pressure is observed by taking direct microscopic photographs varying the moment of exposure, the back pressure, and the ambient density. The results show that the mechanism of spray atomization is divided into 4 processes, and spatial distribution of breakup droplets and a droplet volume rate are assessed for the whole spray region. Total and local distributions of droplet size are expressed by empirical equations as a function of time elapsed from the moment of injection. It is confirmed that the uniformity of the distribution, Sauter mean diameter of droplets, and droplet production rate change with time. Mean droplet diameter is further described in relation to the pressure drop and the ambient density.
Technical Paper

Study on Characteristics of Auto-Ignition and Combustion of Unsteady Synthetic Gas Jet

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.
Technical Paper

Spray and Combustion Characteristics of Reformulated Biodiesel with Mixing of Lower Boiling Point Fuel

Authors propose the reformulation technique of physical properties of Biodiesel Fuel (BDF) by mixing lower boiling point fuels. In this study, waste cooking oil methyl ester (B100), which have been produced in Kyoto city, is used in behalf of BDF. N-Heptane (C7H16) and n-Dodecane (C12H26) are used as low and medium boiling point fuel. Mixed fuel of BDF with lower boiling point fuels have lighter quality as compared with neat BDF. This result is based on the chemical-thermo dynamical liquid-vapor equilibrium theory. This paper describes fundamental spray and combustion characteristics of mixed fuel of B100 with lower boiling point fuels as well as the reformulation technique. By mixing lower boiling point fuel, lighter quality fuels can be refined. Thus, mixed fuels have higher volatility and lower viscosity. Therefore, vaporization of mixed fuel spray is promoted and liquid phase penetration of mixed fuel shortens as compared with that of neat BDF.
Technical Paper

Soot formation/oxidation and fuel-vapor concentration in a DI diesel engine using laser-sheet imaging method

Four kinds of optical measurements were performed to investigate the process of soot formation and oxidation in a direct-injection (DI) diesel engine. Measurements were carried out in an optically accessible DI diesel engine that allows planar laser sheet for combustion diagnostics to enter the combustion chamber either horizontally or along the axis of the fuel jet. The temporal and spatial distribution of soot particles has been investigated using the laser- induced incandescence (LII) and high-speed direct photography. Fuel vapor concentration, which is directly linked to the soot formation process in diesel combustion, has been deduced from the images obtained by the measurements of laser shadowgraph and elastic Mie scattering. According to the experimental results, soot formation begins to occur near the injector nozzle in which a fuel-rich mixture is distributed with a homogeneous condition. LII signal is dominated by the fuel vapor concentration in initial combustion period.
Technical Paper

Soot Kinetic Modeling and Empirical Validation on Smokeless Diesel Combustion with Oxygenated Fuels

This paper provides new insights on the mechanism of the smokeless diesel combustion with oxygenated fuels, based on a combination of soot kinetic modeling and optical diagnostics. The chemical effects of fuel compositions, including aromatics - paraffins blend, neat oxygenated fuels and oxygenate additives, on sooting equivalence ratio ‘ϕ’ - temperature ‘T’ dependence were numerically examined using a detailed soot kinetic model. To better understand the physical factors affecting soot formation in oxygenated fuel sprays, the effects of injection pressure and ambient gas temperature on the flame lift-off length and relative soot concentration in oxygenated fuel jets were experimentally investigated. The computational results show that the leaner mixture side of soot formation peninsula on the ϕ - T map, rather than the lower temperature one, should be utilized to suppress the formation of PAHs and ultra-fine particles together with the large reduction in particulate mass.
Journal Article

Simultaneous Reduction of Pressure Rise Rate and Emissions in a Compression Ignition Engine by Use of Dual-Component Fuel Spray

Ignition, combustion and emissions characteristics of dual-component fuel spray were examined for ranges of injection timing and intake-air oxygen concentration. Fuels used were binary mixtures of gasoline-like component i-octane (cetane number 12, boiling point 372 K) and diesel fuel-like component n-tridecane (cetane number 88, boiling point 510 K). Mass fraction of i-octane was also changed as the experimental variable. The experimental study was carried out in a single cylinder compression ignition engine equipped with a common-rail injection system and an exhaust gas recirculation system. The results demonstrated that the increase of the i-octane mass fraction with optimizations of injection timing and intake oxygen concentration reduced pressure rise rate and soot and NOx emissions without deterioration of indicated thermal efficiency.
Technical Paper

Reduction of Reaction Mechanism for n-Tridecane Based on Knowledge of Detailed Reaction Paths

n-Tridecane is a low boiling point component of gas oil, and has been used as a single-component fuel for diesel spray and combustion experiments. However, no reduced chemical kinetic mechanisms for n-tridecane have been presented for three-dimensional modeling. A detailed mechanism developed by KUCRS (Knowledge-basing Utilities for Complex Reaction Systems), contains 1493 chemical species and 3641 reactions. Reaction paths during ignition process for n-tridecane in air computed using the detailed mechanism, were analyzed with the equivalence ratio of 0.75 and the initial temperatures of 650 K, 850 K, and 1100 K, which are located in the cool-flame dominant, negative-temperature coefficient, and blue-flame dominant regions, respectively.
Technical Paper

Organized Structure and Motion in Diesel Spray

This paper deals with the particle distribution in Diesel spray under the non-evaporating condition from the analytical aspect based on our experimental results. In the analysis, TAB method of KIVA II code and the k-ε turbulent model were used, and the mono-disperse distribution of the initial parcel's diameter, whose size equals to the nozzle hole diameter, was utilized in conjunction with the breakup model. The size distribution of atomized droplets (i.e. the χ-squared distribution function) is justified with the degree of freedom. It is shown that the ambient gas, which is initially quiescent, is induced and led to a turbulent gas jet. The turbulent gas jet which has a equivalent momentum with the Diesel spray was also examined by Discrete Vortex method. The quantitative jet growth was shown to be possible for the estimation and determination in its initial boundary values at the nozzle.
Technical Paper

On-Board Measurement of Engine Performance and Emissions in Diesel Vehicle Operated with Bio-diesel Fuel

This paper describes the results of on-board measurement of engine performance and emissions in diesel vehicle operated with bio-diesel fuels. Here, two waste-cooking oils were investigated. One fuel is a waste-cooking oil methyl esters. This fuel is actually applied to a garbage collection vehicle with DI diesel engine (B100) and the city bus (B20; 80% gas oil is mixed into B100 in volume) as an alternative fuel of gas oil in Kyoto City. Another one is a fuel with ozone treatment by removing impurities from raw waste-cooking oils. Here, in order to improve the fuel properties, kerosene is mixed 70% volume in this fuel. This mixed fuel (i-BDF) is applied into several tracks and buses in Wakayama City. Then, these 3 bio-diesel fuels were applied to the on-board experiments and the results were compared with gas oil operation case.
Technical Paper

NO Formation in Transient Premixed Combustion Field by LIF

In the internal combustion engines, combustion characteristics relating to HC & NO emission are affected remarkably by the spatial distribution of fuel concentration, temperature and turbulence properties. Especially, No formation process inside the combustion chamber affected by the mixture concentration field should be focused relating to the flame field temperature distribution. As the first step of NO formation study in premixed combustion field, NO formation process in the chamber was examined by considering OH radical property and flame temperature in homogeneous mixture conditions. In this study, in order to clarify NO formation process inside the transient premixed combustion field, relative concentration fields of OH radical and NO and temperature fields were measured by laser induced fluorescence technique(LIF) in the constant volume vessel for methane-air homogeneous mixture with the variation of equivalent ratio of the mixture.
Technical Paper

Multicomponent Fuel Consideration for Spray Evaporation Field and Spray-Wall Interaction

It is expected that the analysis of the evaporation process for multicomponent fuels such as actual fuels like gasoline and diesel gas oil could be performed to assess more accurately the mixture preparation field inside the cylinder of D.I.S.I engines and diesel engines. In this paper, we suggested the importance of this multicomponent fuel consideration relating to the mixture formation and combustion characteristics from the basis of their own fuel physical and chemical properties. Then, we introduce a treatment for the phase change of a multicomponent solution through the formation of two-phase regions with the basis of chemical-thermodymical liquid-vapor equilibrium. Next, we analyze the distillation properties of a multicomponent fuel as well as the evaporation process of a multicomponent single droplet by use of the chemical-thermodymical analysis.
Technical Paper

Modelling of Atomization Process in Flash Boiling Spray

This paper presents the analysis of atomization and vaporization processes in a flash boiling spray based on experimental results obtained from injection systems in the suction manifold of a gasoline engine. Two kinds of liquid fuel, n-Pentane and n-Hexane, were injected into quiescent atmosphere at room-temperature and low-pressure through a pintle type injector with electronic control. The spray characteristics of both fuels below various atmospheric pressures were investigated in detail by taking photography. Then, in the region of flash boiling, where the back pressure was below the saturated vapor pressure of fuel, the bubble nucleation process due to the flash boiling was modelled by both the measurement results of bubble and the nucleation rate equation using the degree of superheat of the liquid fuel.
Technical Paper

Modeling and Measurement on Evaporation Process of Multicomponent Fuels

In previous multi-dimensional modeling on spray dynamics and vapor formation, single component fuel with pure substance has been analyzed to assess the mixture formation. Then it should be expected that the evaporation process could be performed for the multicomponent fuel such as actual Gasoline and Diesel gas oil. In this study, vapor-liquid equilibrium prediction was conducted for multicomponent fuels such as 3 and 10 components mixed solution with ideal solution analysis and non-ideal solution analysis. And the computation of distillation characteristics was conducted for the steady state fuel condition fuel condition to understand the evaporation process. As a result, calculated distillation characteristics are consistent well with experiment results. And the evaporation process of a multicomponent droplet in the combustion chamber has been calculated with the variation of ambient pressure and temperature.
Technical Paper

Modeling Atomization and Vaporization Processes of Flash-Boiling Spray

Flash-boiling occurs when a fuel is injected to a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel. It has been known that flashing is a favorable mechanism for atomizing liquid fuels. On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years. In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in fuel spray, when they are injected into the combustion chamber of an internal combustion engine under high pressure. In addition, fuel design concept the multicomponent fuel with high and low volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in internal combustion engine. It is found that the multicomponent fuel produce flash-boiling with an increase in the initial fuel temperature.
Technical Paper

Mixing and soot formation processes in transient gas jet flame

A transient gas jet and its flame are the most fundamental phenomena of a transient spray and its flame breaking out in a CI engine and an SI engine with the direct injection system. In the case of CNG and LNG engines, the fuel itself is just gaseous state. The 2-LIF technique was applied to the transient gas jet to obtain the mixing process between the surroundings and it, and the simultaneous application of LII and LIS techniques were applied to the transient gas jet flame to obtain the soot formation process.
Technical Paper

Mechanism of Combined Combustion of Premixed Gas and Droplets

In an SI engine with direct injection of gasoline (DGI), many small droplets disperse in premixed gas in the cylinder. In a CI engine, diesel spray is injected a cylinder, thus, the situation at the spray periphery is almost the same as that of DGI SI engine. From the standpoint it is useful for understanding the combustion phenomena in both engines to experiment the combined combustion of premixed gas where many small droplets exist. This paper describes this kind of combustion and it seems to be able to apply the results to the simulation of combustion in these engines.
Technical Paper

Low Emission Diesel Combustion System by Use of Reformulated Fuel with Liquefied CO2 and n-Tridecane

We propose a new concept on simultaneous reduction of NO and soot emissions in Diesel engine exhaust by use of the diesel fuel oil (n-Tridecane) with liquefied CO2 dissolved. The CO2 dissolved component is expected to undergo flash boiling or gas separation when being injected into the combustion chamber, and improve spray atomization and mixing process both of which are primary factors to govern soot formation. Further, the internal EGR effect caused by CO2 component injected with the fuel is expected for NO formation. In order to assess this concept, spray dynamics measurement was conducted in the constant volume vessel with a variation of ambient pressure and temperature. Further, combustion experiments were carried out by using a rapid compression and expansion machine. Here, characteristics of the evaporative mixed fuel spray were examined by shadowgraph photography.